If Back to the Future använder olika tidslinjer, varför började Marty blekna?

"Jag tycker att det är väletablerat att för grundprincipen i Back to Future Trilogy att arbeta, har vi ett system med alternativa tidslinjer."

Om "alternativa tidslinjer" menar samstämmiga parallella tidslinjer, så att "tidigare" tidslinje inte raderas när den "nya" tidslinjen skapas, då nej, använder inte Back to the Future den teorin. Istället använder den modellen av en enda tidslinje som kan skrivas om varje gång en förändring görs, och denna omskrivning kan göra att världen förvandlas runt tiden genom rippelverkan (som vad hände när Jennifer lämnades på verandaen i ändrade "1985-A" och Doc berömde Marty genom att säga "Oroa dig inte Marty, om vi lyckas med vårt uppdrag, kommer detta alternativ 1985 att ändras tillbaka till den verkliga 1985en, som omedelbart omvandlas kring Jennifer och Einie.") I vissa fall, denna krusande förändring till tidslinjen kan också radera en tid resenär från existens, i fall där de inte borde ha fötts på den ändrade tidslinjen, eller borde ha levt till sin nuvarande ålder. Allt detta görs tydligt i Officiella tillbaka till framtiden FAQ av skaparna Bob Gale och Robert Zemeckis, när de prata om varför gammal Biff ursprungligen var planerad att börja bleka när han återvände till 2015, och också varför han återvände till samma 2015 som Marty, Doc och Jennifer var i, istället för att de återstod i "original" 2015 medan gamla Biff återvänder till en alternativ 2015-A (framtiden för den heliga 1985-A skapad av hans givande av hans yngre själv sportalmanacen 1955) som du skulle förvänta dig i den samtidiga parallella tidslinje teorin:

1.8: What happened to old Biff when he staggered out of the DeLorean in 2015?

The Secrets of the Back to the Future Trilogy A: Our intention regarding old Biff was that upon his return to 2015, he would be erased from existence because he had changed his entire destiny by giving his younger self the Sports Almanac. (Probably, Lorraine shot him sometime around 1996!). After old Biff clutches his chest and staggers (the same symptoms that Marty exhibited in Back to the Future when he was beginning to be "erased"), we actually filmed him falling onto the street and vanishing, and we previewed the movie this way (see The Secrets of the Back to the Future™ Trilogy). However, the vast majority of the audience did not understand it, so we decided to cut it out, leaving the answer ambiguous, and subject to various interpretations — besides the above explanation, you can believe that Old Biff had a heart attack from the shock of time travel of from flying the car, or from something that happened to him in 1955.

1.9: When Doc and Marty are in 1955-A, Doc says they can't return to the future to stop Biff from stealing the DeLorean, because it would be the wrong future. But if that's true, how did Old Biff manage to get back to the same future that he left? Shouldn't he have come back to a different future?

A: As should be clear from the answer to the previous question, we believe Old Biff DID indeed return to a different future — a "2015-A," which would have transformed around Marty, Doc, Jennifer and Einstein (just as Doc explains how 1985-A would change into 1985 and instantly transform around Jennifer and Einstein). This would happen AFTER Old Biff returned with the DeLorean. For this reason, we made sure that Doc had caught Jennifer and exited the McFly Townhouse before Old Biff returned. Thus, by the time Marty and Doc are carrying Jennifer back to the DeLorean, there COULD be other residents in that townhouse — or perhaps the McFlys still live there. It is just as believable that the physicality of the neighborhood did NOT change as it is to believe that it did — so we didn't change it. We decided not to make anything of this idea because this is one of those difficult time travel concepts that general audiences have a real hard time understanding. (Try explaining this stuff to your mother and you'll see what we mean.) A detailed explanation of it would have slowed down the story, and most of the audience doesn't ever think about it. That's why we made certain things ambiguous and left various things open for interpretation in hopes that the possibility of at least one or two explanations would be better than a "definitive" explanation that you could find holes in. Let's face it, time travel is fantasy, so there's no way to "prove" anything. As filmmakers, we try to create a set of rule for our stories and stick by them, and stay consistent within the little "universe" that we've created.